Motor Cortex Of The Brain: Parts, Location And Functions
Greets. Smile. Kiss. Runs. Eat. All of these actions have at least one aspect in common: they require some type of movement on the part of the subject to be carried out. The ability to move is essential for survival, since it allows us to react to stimuli and actually execute any type of behavior, including those necessary to allow our survival. But movement does not just happen, it requires some planning, coordination and precision.
At the level of the brain, this control It is carried out mainly by the motor cortex of the brain, although it is also influenced and mediated by other brain structures. Throughout this article we can see what the motor area is, where it is located and what parts it consists of, as well as some of the main problems that arise when injured.
The motor or motor area of the brain is that part of the cerebral cortex whose main functions are to allow the generation, maintenance and termination of voluntary and conscious movements by the subject.
This brain region is located in the upper and rostral part of the brain, in the posterior part of the frontal lobe, located just before the central or Rolando fissure and the somatosensory area. It is in this area where Penfield’s motor homunculus is represented, a representation that indicates the parts of the cortex focused on the movement of certain muscles among which some especially innervated ones stand out, such as the hands, the tongue or the face.
Within the motor cortex we can find different regions, all of them of great importance when it comes to managing movement. Among them the main ones are the following.
1. Primary motor cortex
The main structure in charge of movement is the area that will generate and send the movement order to all the voluntary muscles of the body. It is the part of the brain that sends the order to the muscles to contract or tense generating movement.
The primary motor cortex does not work alone, but requires information from the following areas to be able to plan and develop movements. In the primary motor cortex there are, among others, Beltz cells. These long cells, which will go through the spinal cord to make synapses with other motor neurons.
2. Secondary motor cortex
This area has an important role when it comes to programming and planning the movements and sequences to follow in order to be able to carry out the movements in a precise and coordinated manner. Despite this and the fact that the electrical stimulation of these areas can produce movement, it is not in itself the one that is dedicated to performing them, but focuses on organize movement before the primary motor can carry it out
In order to perform a movement, the action of these areas will first be necessary, in order to later pass the information to the primary motor area and once there, the movement order will be sent. It is very connected to the association areas. Within the secondary motor area we can find two regions of great relevance.
Located in the motor cortex, in front of the primary motor cortex and near the Sylvian fissure, is the premotor area or cortex. This area is especially linked to the programming and guidance of movement, storing motor programs learned through experience. This also includes the movement necessary for speech. It usually acts on those motor responses guided by an exogenous stimulus.
2.2. Supplementary motor area
Part of the secondary motor cortex, the supplementary motor area is associated with planning, programming and coordination in complex movements, as well as the initiation of movement. Also participate in aspects such as adopting positions and also has influence on uncoordinated movements.
3. Drill Area
In different classifications, Broca’s area is included within the motor areas of the brain, since allows language production and the muscle movement necessary for it. It is located on the edge of the supplementary motor area.
4. Association areas of the posterior parietal cortex
In some classifications this area appears as one of the motor areas, because transforms visual and other sensory information into motor instructions
Related problems and disorders
As we have indicated previously, the motor cortex is a brain region of great importance when it comes to being able to carry out practically any action. This is why an injury to these brain areas can have severe repercussions on patients’ lives.
One of the problems that injury or destruction of the cortex or motor area can generate is paralysis and loss of mobility, whether in a specific part of the body, in a hemibody or in the entire body. Hemiplegia or tetraplegia may appear. If the lesion is only in one hemisphere, the paralysis will occur contralaterally: that is, if the right motor cortex is injured, the left hand will be paralyzed.
Regarding secondary motor areas, the effects of an injury to them usually alter the ability to perform movements in a coordinated and sequential manner. We are talking about the emergence of possible apraxias, or aphasias or dysarthrias when we refer to problems in the production of the movements necessary to communicate. Agraphia can also occur not being able to correctly perform the movements necessary to write, eating problems or even visual problems due to not correctly governing the movement of the facial organs and muscles.
